Cross-Reference to Related Applications
This is an original application.
1. Field of Invention
This invention relates generally to ammunition and more particularly to wads for shotshells.
2. Description of the Related Art
Shot wads have been in existence for more than a century, and plastic shot wads have been used in shotshells for several decades. Combination shot cup and over powder wads have been used for more that 25 years. One piece shot wads such as the Winchester AA are widely known and used. Most existing collapsible shot wads have a hinge section which collapses to roughly 50% of the initial height. With the recent change from lead shot to steel shot in many shooting areas due to environmental concerns over lead, the space in shotshells has become much tighter due to the larger volume of steel shot needed to produce equivalent results.
The collapsible section of a wad is very useful for several reasons. First, it allows some internal adjustment for normal variations in the volume of propellant and shot charged into a shell by conventional loading equipment and thus gives more consistent shotshell closures or crimps. Secondly, the additional volume created by the collapsing of the wad slows the very rapid pressure buildup upon firing and thus lowers the resultant peak pressure. In shotshell ammunition where load performance is constrained by peak pressure levels, this pressure mitigation can be used to achieve higher velocities with a given propellant or to allow the use of a faster, cleaner burning propellant to achieve the same velocities. For target shooting, the slower pressure rise and lower peak pressure results in softer felt recoil, which can help with accuracy and comfort, especially in competitive shooting where hundreds of shots may be 10 fired in a day.
A new technical approach is needed which can allow more collapse in limited space to increase the benefit of collapsibility in the smaller axial wad space available in modern shotshells.